Interlacing and non-interlacing (or progressive) image scanning and displaying techniques are widely applied to a variety of systems. Thus, when an image is transmitted between systems or for display, conversion between interlacing and non-interlacing formats is often required.
Please refer to FIG. 1 which schematically illustrates a de-interlacing processing. An odd field 11 and an even field 12 to be de-interlaced are shown, each including a half of scan lines of a scanned image. After a de-interlacing operation 13, a non-interlaced frame 14 is obtained, which includes all scan lines, as shown in FIG. 1. The odd field 11 comprises first scan line 111, third scan line 113, fifth scan line 115, and so on. The even field 12 comprises second scan line 122, fourth scan line 124, sixth scan line 126, and so on. After the de-interlacing operation 13, a non-interlacing frame 14 is obtained, including all scan lines 141, 142, 143, 144, 145, 146, . . . of the scanned image corresponding to the interlaced lines 111, 122, 113, 124, 115, 126, . . . respectively.
The de-interlacing operation 13 is implemented with interpolation. That is, data of the missing lines in the odd field 11 or even field 12 are estimated by way of interpolation. Two kinds of interpolating algorithms may be applied to the de-interlacing operation. One is spatial interpolation, and the other is temporal interpolation. The spatial interpolation calculates the missing even lines or odd lines by interpolating corresponding adjacent lines in the odd field 11 or the even field 12 respectively. For example, the even scan line 144 of the non-interlacing frame 14 can be obtained by interpolating the scan lines 113 and 115 in the odd field 11. Similarly, the entire non-interlacing frame 14 can be obtained by interpolating every pair of adjacent lines in the odd field 11. On the other hand, the temporal interpolation method fills the missing lines with corresponding lines in the preceding field. For example, the odd scan line 113 in the odd field 11 can be used to fill the missing odd scan line between the even scan lines 122 and 124 of the even field 12. Accordingly, the entire non-interlacing frame 14 is obtained with the even scan lines 122, 124, 126, . . . in the even field 12 serving as the even scan lines 142, 144, 146, . . . and the odd scan lines 111, 113, 115, . . . obtained at the preceding time point serving as the odd scan lines 141, 143 and 145, . . . .
By taking advantage of both the interpolation methods, a motion adaptive de-interlacing algorithm is developed. A level of motion is determined by performing motion-detection in each field. Then a proper de-interlacing algorithm and its corresponding ratio are chosen according to the obtained levels of motion. An exemplary motion adaptive de-interlacing system used in a computer system is shown in FIG. 2. The motion adaptive de-interlacing system comprises a motion-detection module 21 for performing two-level motion-detection according to a current field F(n), preceding field F(n−1) and next field F(n+1). The motion-detection module 21 also generates a control signal to control a multiplexer 22 to select one of the outputs from a spatial interpolation module 23 and a temporal interpolation module 24, then the selected output is integrated with the current field F(n) as a non-interlacing frame 25.
Generally speaking, for motion images, spatial interpolation will produce better quality than temporal interpolation. This is because the spatial interpolation module 23 does not consider the preceding field F(n−1). On the contrary, temporal interpolation will have better performance than spatial interpolation for still images. Consequently, the spatial interpolation module 23 and the temporal interpolation module 24 selectively function depending on the practical use.
To perform the motion-detection, a conventional computer system requires additional motion-detection module 21 in order to detect the level of motion of the current field F(n). Complexity of the motion-detection-module 21 may grow large as the levels of motion to be detected increases. It is apparently disadvantageous in hardware cost of the computer system.